Excessive excitation by neurotransmitters can cause the degeneration and death of neurons. It is believed that this degeneration is in part mediated by the excitotoxic actions of glutamate and aspartate at the N-methyl-D-aspartate (NMDA) receptor. This excitotoxic action is responsible for the loss of neurons in cerebrovascular disorders such as: cerebral ischemia or cerebral infraction resulting from a range of conditions such as thromboembolic or hemorrhagic stroke, cerebral vasospasm, hypoglycemia, cardiac arrest, status epilepticus, perinatal asphyxia, cerebral trauma and anoxia (such as from drowning and pulmonary surgery).
There are no specific therapies for these neurodegenerative diseases, however, compounds which act specifically as antagonists of the NMDA receptor complex, either competitively or noncompetitively, offer a novel therapeutic approach to these disorders: R. Schwarcz and B. Meldrum, The Lancet 140 (1985); B. Meldrum in "Neurotoxins and Their Pharmacological Implications" edited by P. Jenner, Raven Press, New York (1987); D. W. Choi, Neuron 1:623 (1988). Confirmation of the protective effects of noncompetitve NMDA antagonists in various pharmacological models of neurodegenerative disorders have appeared in the literature: J. W. McDonald, F. S. Silverstein, and M. V. Johnston, Eur. J. Pharmocol. 140:359 (1987); R. Gill, A. C. Foster, and G. N. Woodruff, J. Neurosci. 7:3343 (1987); S. M. Rothman, J. H. Thurston, R. E. Hauhart, G. D. Clark, and J. S. Soloman, Neurosci. 21:673 (1987); M. P. Goldbert, P-C. Pham, and D. W. Choi, Neurosci. Lett. 80:11 (1987) L. F. Copeland, P. A. Boxer, and F. W. Marcoux, Soc. Neurosci. Abstr. 14 (part 1):420 (1988); J. A. Kemp, A. C. Foster, R. Gill, and G. N. Woodruff, TIPS 8:414 (1987); R. Gill, A. C. Foster, and G. N. Woodruff, J. Neurosci. 25:847 (1988); C. K. Park, D. G. Nehls, D. I. Graham, G. M. Teasdale, and J. M. McCulloch, Ann. Neurol. 24:543 (1988); G. K. Steinburg, C. P. George, R. DeLaPlaz, D. K. Shibata, and T. Gross, Stroke 19:1112 (1988); J. F. Church, S. Zeman, and D. Lodge, Anesthesiology 69:702 (1988).
The compounds of the present invention are useful in the treatment of neurodegenerative disorders including cerebrovascular disorders. Such disorders include but are not limited to cerebral ischemia or cerebral infarction resulting from a range of conditions such as thromboembolic or hemorrhagic stroke, cerebral vasospasm, hypoglycemia, cardiac arrest, status epilepticus, perinatal asphyxia, cerebral trauma and anoxia such as from drowning and/or pulmonary surgery. Other treatments are for schizophrenia, epilepsy, spasticity, neurodegenerative disorders such as Alzheimer's disease or Huntington's disease, Olivo-pontocerebellar atrophy, spinal cord injury, and poisoning by exogenous NMDA poisons (e.g., some forms of lathyrism). Further uses are as analgesics and anesthetics, particularly for use in surgical procedures where a finite risk of cerebrovascular damage exists.